Abstract
We have calculated the condensation and evaporation of ternary CH4-N2-C2H6 liquid drops and solid CH4 hail as they fall through Titan's lower atmosphere to determine the likelihood that precipitation reaches the ground. Assuming the humidity profile determined by the Huygens probe, binary liquid CH4/N2 condensate grows in the region from ∼8 to 15 km in Titan's atmosphere because the combined humidity of CH4 and N2 exceeds saturation. These drops evaporate below ∼8 km. We determine the fate of 10 μm seeds composed of ethane, which is expected to provide condensation sites. In addition, we study the fate of already formed raindrops with radii of 1-4.75 mm falling out of the growth region. High (50%) and low (0%) ethane relative humidities (RH) are considered in the calculation. We find that drops with radii ∼3 mm and smaller dropping from 8 km reach the ground in compositional equilibrium with the atmosphere in the high ethane RH case as a result of the stabilizing influence of the ethane, and evaporate in the atmosphere in the low ethane RH case. Large drops (>∼3 mm) reach the surface large and cold because the latent heat loss due to the evaporation of methane cools the drop and slows the evaporation rate. Pure methane hail hits the ground if its radius is initially more than 4 mm at 16 km above the surface and sublimates in the atmosphere if its radius is smaller.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 346-357 |
| Number of pages | 12 |
| Journal | Planetary and Space Science |
| Volume | 56 |
| Issue number | 3-4 |
| DOIs | |
| State | Published - Mar 2008 |
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Keywords
- Hail
- Huygens
- Methane
- Rain
- Titan
ASJC Scopus subject areas
- Geophysics
- Space and Planetary Science
- Astronomy and Astrophysics
Cite this
Rain and hail can reach the surface of Titan. / Graves, S. D B; McKay, C. P.; Griffith, Caitlin; Ferri, F.; Fulchignoni, M.
In: Planetary and Space Science, Vol. 56, No. 3-4, 03.2008, p. 346-357.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Rain and hail can reach the surface of Titan
AU - Graves, S. D B
AU - McKay, C. P.
AU - Griffith, Caitlin
AU - Ferri, F.
AU - Fulchignoni, M.
PY - 2008/3
Y1 - 2008/3
N2 - We have calculated the condensation and evaporation of ternary CH4-N2-C2H6 liquid drops and solid CH4 hail as they fall through Titan's lower atmosphere to determine the likelihood that precipitation reaches the ground. Assuming the humidity profile determined by the Huygens probe, binary liquid CH4/N2 condensate grows in the region from ∼8 to 15 km in Titan's atmosphere because the combined humidity of CH4 and N2 exceeds saturation. These drops evaporate below ∼8 km. We determine the fate of 10 μm seeds composed of ethane, which is expected to provide condensation sites. In addition, we study the fate of already formed raindrops with radii of 1-4.75 mm falling out of the growth region. High (50%) and low (0%) ethane relative humidities (RH) are considered in the calculation. We find that drops with radii ∼3 mm and smaller dropping from 8 km reach the ground in compositional equilibrium with the atmosphere in the high ethane RH case as a result of the stabilizing influence of the ethane, and evaporate in the atmosphere in the low ethane RH case. Large drops (>∼3 mm) reach the surface large and cold because the latent heat loss due to the evaporation of methane cools the drop and slows the evaporation rate. Pure methane hail hits the ground if its radius is initially more than 4 mm at 16 km above the surface and sublimates in the atmosphere if its radius is smaller.
AB - We have calculated the condensation and evaporation of ternary CH4-N2-C2H6 liquid drops and solid CH4 hail as they fall through Titan's lower atmosphere to determine the likelihood that precipitation reaches the ground. Assuming the humidity profile determined by the Huygens probe, binary liquid CH4/N2 condensate grows in the region from ∼8 to 15 km in Titan's atmosphere because the combined humidity of CH4 and N2 exceeds saturation. These drops evaporate below ∼8 km. We determine the fate of 10 μm seeds composed of ethane, which is expected to provide condensation sites. In addition, we study the fate of already formed raindrops with radii of 1-4.75 mm falling out of the growth region. High (50%) and low (0%) ethane relative humidities (RH) are considered in the calculation. We find that drops with radii ∼3 mm and smaller dropping from 8 km reach the ground in compositional equilibrium with the atmosphere in the high ethane RH case as a result of the stabilizing influence of the ethane, and evaporate in the atmosphere in the low ethane RH case. Large drops (>∼3 mm) reach the surface large and cold because the latent heat loss due to the evaporation of methane cools the drop and slows the evaporation rate. Pure methane hail hits the ground if its radius is initially more than 4 mm at 16 km above the surface and sublimates in the atmosphere if its radius is smaller.
KW - Hail
KW - Huygens
KW - Methane
KW - Rain
KW - Titan
UR - http://www.scopus.com/inward/record.url?scp=39549097541&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=39549097541&partnerID=8YFLogxK
U2 - 10.1016/j.pss.2007.11.001
DO - 10.1016/j.pss.2007.11.001
M3 - Article
AN - SCOPUS:39549097541
VL - 56
SP - 346
EP - 357
JO - Planetary and Space Science
JF - Planetary and Space Science
SN - 0032-0633
IS - 3-4
ER -